drm/amd/display: Fix DPIA outbox timeout after GPU reset

[Why]
The HW interrupt gets disabled after GPU reset so we don't receive
notifications for HPD or AUX from DMUB - leading to timeout and
black screen with (or without) DPIA links connected.

[How]
Re-enable the interrupt after GPU reset like we do for the other
DC interrupts.

Fixes: 81927e28 ("drm/amd/display: Support for DMUB AUX")

Reviewed-by: Jude Shih <Jude.Shih@amd.com>
Acked-by: Qingqing Zhuo <qingqing.zhuo@amd.com>
Signed-off-by: Nicholas Kazlauskas <nicholas.kazlauskas@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>